Role of a propeller loop in the quaternary structure and enzymatic activity of prolyl dipeptidases DPP-IV and DPP9

Abstract

a b s t r a c tThe dipeptidyl peptidase (DPP) family members, including DPP-IV, DPP8, DPP9 and others, cleave the peptide bond after the penultimate proline residue and are drug target rich. The dimerization of DPP-IV is required for its activity. A propeller loop located at the dimer interface is highly conserved within the family. Here we carried out site-directed mutagenesis on the loop of DPPIV and identified several residues important for dimer formation and enzymatic activity. Interestingly, the corresponding residues on DPP9 have a different impact whereby the mutations decrease activity without changing dimerization. Thus the propeller loop seems to play a varying role in different DPPs. Structured summary of protein interactions:DPP-IV and DPP-IV physically interact by comigration in gel electrophoresis (View interaction: 1, 2, 3, 4) DPP9 and DPP9 bind by circular dichroism (View interaction) DPP-IV and DPP-IV bind by circular dichroism (View interaction: 1, 2, 3, 4, 5) DPP-IV and DPP-IV bind by cosedimentation in solution (View interaction: 1, 2, 3, 4, 5) ADA binds to DPP-IV by surface plasmon resonance (View interaction: 1, 2, 3, 4, 5, 6) DPP9 and DPP9 bind by cosedimentation in solution (View interaction)

A Novel SUMO1-specific Interacting Motif in Dipeptidyl Peptidase 9 (DPP9) That Is Important for Enzymatic Regulation

“…However, they found that the arm of DPP9 was not essential for dimerization, because a DPP9 construct lacking a large part of the predicted arm (amino acids corresponding to Ile 288 -Tyr 305 ) is correctly folded and forms dimers. Interestingly, the deletion mutant was less active compared with the wild-type protein (50). The reason for the reduced activity is currently not understood.…”

“…Recently, Tang et al (50) showed that DPPIV mutants, deleted of the arm motif fail to dimerize and are less active. However, they found that the arm of DPP9 was not essential for dimerization, because a DPP9 construct lacking a large part of the predicted arm (amino acids corresponding to Ile 288 -Tyr 305 ) is correctly folded and forms dimers.…”

“…The deletion mutant of DPP9 reported by Tang et al (50) only partially covers the SUBA, because it does not include valine 285, which shows the most dramatic loss in interaction with SUMO1 if replaced by an alanine. Therefore, we tested both the activity of the DPP9V285A mutant, and its ability to form dimers as the wild-type enzyme.…”

Advances in Understanding the Expression and Function of Dipeptidyl Peptidase 8 and 9

“…Given that the crystal structures of DPP8 and DPP9 have not yet been solved, protein homology modeling has shown that DPP8 and DPP9 likely share a similar tertiary structure with DPPIV and FAP (32,33). DPP8 (34) and DPP9 (35) are dimeric, with each monomer likely consisting of an a/b-hydrolase domain and an 8 blade b-propeller domain and the active site of the peptidase locates at the interface of these 2 domains (Fig. 2) (3,23).…”

“…Second, single-point mutations in the C-terminal loop, such as F822A, V833A, Y844A, and H859A in DPP8 (34), or F842A in DPP9 (40) inactivate these proteases without disrupting dimerization. Similarly, a deletion mutation (residues 317-334) or a single-point mutation (Y334A) in a propeller loop in DPP9 can cause decreased activity without affecting dimerization (35). Thus, the C-terminal loop and the propeller loop are essential for DPP8 and DPP9 enzyme activity but not for dimerization.…”